This invention relates to a solar battery using amorphous silicon. More particularly, this invention relates to an amorphous silicon solar battery characterized by having an electrode of special structure placed opposite to an electrode passing incident light (hereinafter referred to as "a transparent electroconductive electrode") via amorphous silicon layers (hereinafter said electrode being referred to as "a back electrode").
Growing interest has been shown lately towards solar batteries as a new energy source, and especially great hopes are placed on solar batteries using amorphous silicon. This is based on the facts that solar energy is pollution-free and inexhaustible, and that while the conventional solar batteries such as those using single-crystal silicon were very costly and also limited in their use to specific applications, the amorphous silicon solar battery is considered capable of realizing a drastic cost reduction.
The output voltage of one amorphous silicon solar cell is usually below 1 V, but in practical applications of such devices, it is in many cases required that their output voltage (per unit) be higher than 1 V. For this, it is necessary to connect a plurality of solar cells in series to form a battery. From the standpoint of low-cost production, it is an essential requirement that a required number of these solar cells can be formed in regular succession on the same substate. For connecting a plurality of solar cells in series on the same substrate, it is necessary that the individual cells be electrically isolated from each other. For this purpose, the substrate itself must be an insulator, or in case the substrate is conductive, an insulating film must be formed on its surface.
In order to meet such requirements, a proposal has been made in which a film made of a heat-resistant high-molecular polyimide resin or a metal film having a heat-resistant resin layer on its surface is used as the substrate of an amorphous silicon solar battery. However, the amorphous silicon solar battery of such construction is generally poor in reliability and also involves quality problems, especially in moisture resistance. Because the organic resin used for the electrical insulation in such an amorphous silicon solar battery is permeable to moisture, the back electrode, which is usually made of stainless steel, Al, Cr, Ni-Cr alloy, Mo or the like, is oxidized in prolonged use or when left unused for a long time, causing corrosion of the electrode with resultant degradation of its conductive quality and even peeling of the electrode. Naturally, the output of the solar battery is greatly reduced.